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Calling Yamaha Electrical Gurus! I'm in over my head

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So I picked up a non running 95 yz125 the other day (I know, I know). PO said it had been running well till he splashed through some water and the bike quit. His diagnosis was water had gotten into the stator and shorted it out. As a result, he had asked some friend of his to pull the flywheel and cut the stator coils off. That's how it came to me.

I ordered new coils from RM stator, and just my luck they came with no instructions whatsoever. I was able to find a tutorial elsewhere online, but not for my exact bike so I was sort of flying blind. I basically put the coils in and wired it up going by some poor quality pictures and the way the wires in the case were already bent. It's probably all wrong, but I have nothing to compare it to here. A pic for your viewing pleasure:

DSCN1027.jpg

Up is up, right is right etc.

Anyway, I'm getting a spark but it seems kind of weak, and the bike definitely isn't starting. Getting fuel to the carb and air through the filter, so I'm not sure what's going on here. If it looks like it's wired right (ish), I'll give the PO an earful and or pull the carb or start futzing with other electrical components. Thanks in advance for your assistance.

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I would take a multimeter to all of the electrical components per the shop manual and be sure you are getting the correct readings. Good luck. Water in the stator is fairly common. Mine was pretty bad as well when I took my cover off the other day. :p

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At this point I'm really just trying to determine if I wired it backwards or not. :p

Do you know where I can find this manual you speak of online? Google Books has pieces of the Clymer manual but it's missing the sections I need.

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don't think you'd get any spark, if wiring was wrong, what do you mean by weak spark, is it orange or blue, stupid question, have you tried a new plug? stator coils just trigger the pulse, the ignition coil makes the high voltage, weak spark, is an ign coil, plug lead and boot, or a plug.

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Spark is bluish white but real thin.

Plug looks brand spanking new as I suspect the PO swapped it out after he couldn't fire it up. Could be gapped wrong I suppose.

My thought was that if the coils were wired backwards it would spark but the timing would be so far off it wouldn't fire up...

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i'd be checking the ignition coil and plug wire. the timing is controlled at the pickup and flywheel position. i really suspect the ignition coil, is your problem. should be able to check it w/ on ohmeter.

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Two things I have found with the coil, 1)pull the coil off and clean the frame, most likely there will be some rust - you need a good ground. 2) unscrew the plug boot and clip off a 1/4 inch or so and screw it back on. These are simple and fast to do and just eliminate potential problems.

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Two things I have found with the coil, 1)pull the coil off and clean the frame, most likely there will be some rust - you need a good ground. 2) unscrew the plug boot and clip off a 1/4 inch or so and screw it back on. These are simple and fast to do and just eliminate potential problems.

great advice, and a good place to start.:p

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stator wire connection at coil to plug lead no more than 8 - 10 ohms

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Thanks, it's cold and threatening rain today so I'm not going to be able to dig into this, but I'll be busting out the multimeter shortly.

For now, I really just want to eliminate my wiring as the culprit. Can anybody confirm that the coils are hooked up how they should be? My real concern looking at it is that the soldering points should be on the inside of the coil, not outside or that they should be bolted up going horizontally across the top instead of up and down.

Either way, reconfiguring would change which ends were wired to which leads. I suspect the fact that I'm getting any spark at all means they're bolted up in the right orientation but maybe they need to be flipped. Now I wish I had taken physics in college.

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Ok, busted out the meter and I got a reading of 10.6 kΩ from input to plug lead and .6Ω from input to ground . . . does that sound fubar to you guys? It definitely does not look like an OEM part, probably not even a part for this bike. Somebody fabbed a little bracket so it could even be bolted in place:

DSCN1028.jpg

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sounds like it's wired right,see the screw marks the dark areas beside the screws that hold the stater essembly on,loosen them and turn the essembly till the screws completely cover the dark areas witch most likely is where the original setting was.alo sand the outside sides of flywheel with with 400grit to 600grit to get of any corrosion,dont sand to much just make it shiny then take the little black box sand the metal surface the same,blow every thing clean with compressed air or wipe down,put the flywheel on loosen the screws on the black box thingy,make shure your piston is at "tdc"do this by sticking pencil in sparkplug hole and slowly crank kick starter by hand while feeling the pencil come to it's highest point with your other hand,you might have to try a couple of times,anyhow once at "tdc" pull the black box away from the flywheel slightly and put a receipt from corner store in the gap,push the black box snug against flywheel with reciept in gap tighten the screws,pull out reciept,make shure you have a good battery and sparkplug,give hear a rip:bonk: :)

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alright, found the part of the clymer manual I needed online, followed their testing procedure, and it definitely looks like the coil is out of spec. Will order a new one and report back.

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Ok, busted out the meter and I got a reading of 10.6 kΩ from input to plug lead and .6Ω from input to ground . . . does that sound fubar to you guys? It definitely does not look like an OEM part, probably not even a part for this bike. Somebody fabbed a little bracket so it could even be bolted in place:

DSCN1028.jpg

yea thats a universal aftermarket, the one mount bolt missing caused it to vibrate and self destruct, if going back w/ the same kind secure it well. denniskirk.com has those kind, about 21.00 shipped. i had to use one on an older bike. the oem is probably more.

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The bolt was in there when I got to it, I just decided to snap a pic mid removal. However, because of the way the mount is set up, the ground plate of the coil is clearly bent.

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Well guys, I pulled the whole electrical system apart, cleaned all the contacts, sanded the flywheel and the pickup, cut and reinstalled the plug cap, pulled and cleaned the carb, pulled the pipe off and sealed it with RTV, and sealed up the stator cover. . . .

and . . . SHE RUNS!!!! No idea what did it, but who cares?

Thanks for the help everyone, I definitely needed some coaching but now that I have taken most of the bike apart and put it back together, I feel like I have a much better grasp of what's going on in there.

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Well guys, I pulled the whole electrical system apart, cleaned all the contacts, sanded the flywheel and the pickup, cut and reinstalled the plug cap, pulled and cleaned the carb, pulled the pipe off and sealed it with RTV, and sealed up the stator cover. . . .

and . . . SHE RUNS!!!! No idea what did it, but who cares?

Thanks for the help everyone, I definitely needed some coaching but now that I have taken most of the bike apart and put it back together, I feel like I have a much better grasp of what's going on in there.

yo the man:banana: :thumbsup:

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Yeah, tough to say. I really just did everything I could think of, put it back together and braaap.

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